The invention relates to a motor vehicle having a side sill made of sheet metal, having an inner shell connected to an outer shell by upper and lower flanges.
Use of an inner shell and an outer shell to construct a side sill of a motor vehicle according to shell construction is generally known. For cost reasons the outer shell is frequently designed as one piece with a side wall of the motor vehicle. The side wall typically extends from the side sill to the roof side frame, and at least over the entire side door aperture of the motor vehicle.
In recent times, use of high-strength sheet steel has become more prevalent in body construction for the purpose of reducing weight and increasing rigidity. However, high-strength sheet steel permits only slightly more shaping than conventional sheet steel before reaching its yield point. During deep-drawing of high-strength sheet steel, the yield point is reached at comparatively small shaping paths. High-strength sheet steel tears when shaping is performed beyond the yield point. For this reason, until recently it was not possible to manufacture side walls having an integrated outer shell of the side sill from high-strength sheet steel, since the permissible shaping paths are too small.
A method is known from German Patent Document DE 101 28 989 A1 for forming a side wall as one piece with an outer shell of a side sill from high-strength sheet steel. In this case, the side wall merges without gradation into the adjoining side sill in the region of at least one vehicle pillar. As a result of the gradation being omitted, and therefore as a result of the lack of unrestricted overstrain of the sheet steel during the drawing process, the sheet steel is subjected to significantly less strain. Therefore, sheet steel having a higher yield point may be used.
The exemplary embodiments of the invention describe methods and systems to produce a motor vehicle having a side sill of shell construction which is partially formed by a side wall which may be composed of high-strength sheet steel.
According to an embodiment of the invention, a motor vehicle has a side sill of sheet metal shell construction having at least one inner shell and one outer shell which are connected to one another by an upper and a lower flange. The exemplary outer shell may be formed by the lower section of a side wall to which an outer panel is attached for providing a downward extension, so that the inner shell and the outer panel are connected to one another in the lower flange. The inner shell and the side wall thus are connected to one another in the upper flange.
The drawing depth required for a side wall having an integrated outer shell of a side sill is determined primarily by the width of the side sill. As a result of the division of the outer shell of the side sill on the side wall and a separate outer panel, only very small drawing depths are necessary for the side wall, regardless of the shape and width of the side sill. The shape and width of the side sill essentially affect only the shape and drawing depth of the outer panel. For this reason, the exemplary side wall may have small drawing depths of less than 85 mm, independent of the design of the side sill. This allows the use of sheet steel of high material quality for the side wall, having an Rp02 yield point of, for example, about 160 MPa or greater. On account of the smaller draw depth, the manufacture of the side wall is simplified to the extent that even the panel thickness of the side wall may be reduced. Thus, for example, panel thicknesses of about 0.7 mm and less may be achieved. The material quality and thickness of the outer panel may be functionally designed independently of the side wall. On the whole, the division of the outer shell of the side sill on the side wall and the separate outer panel afford greater design flexibility. Thus, the width of the side sill is no longer limited by manufacturability concerns, and the side sill may have localized drawn-in areas.
The side wall and the outer panel, according to an embodiment of the invention, preferably form an overlap region in the form of a connecting flange. Multiple spot welding connections are particularly suited for joining the side wall to the outer panel.
The side sill may be advantageously cladded with a panel on the visible vehicle exterior. For this reason the outer panel need not have attractive visible surfaces of appropriate surface quality. In addition, the connecting flange between the side wall and the outer panel is no longer visible, and is protected from the effects of dirt and water spray. The panel may be designed as a plastic component, for example.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.